The risk of prostate cancer on incidental finding of an avid prostate uptake on 2-deoxy-2-[ 18 F]fluoro-d-glucose positron emission tomography/computed tomography for non-prostate cancer-related pathology: A single centre retrospective study.

OBJECTIVE: To review the risk of prostate cancer (PCa) in men with incidentally reported increased intraprostatic uptake at 2-deoxy-2-[18 F]fluoro-d-glucose positron emission tomography/computed tomography (18 F-FDG PET/CT) ordered at Department of Urology, The Wesley Hospital, Brisbane, QLD, Australia for non-PCa related pathology.

METHODS: Retrospective analysis of consecutive men between August 2014 and August 2019 presenting to a single institution for 18 F-FDG PET/CT for non-prostate related conditions was conducted. Men were classified as benign, indeterminate, or malignant depending of the results of prostate-specific antigen (PSA), PSA velocity, biopsy histopathology, and three-Tesla (3 T) multiparametric MRI (mpMRI) Prostate Imaging Reporting and Data System score, or gallium-68-prostate-specific membrane antigen (68 Ga-PSMA) PET/CT results.

RESULTS: Three percent (273/9122) of men demonstrated 18 F-FDG avidity within the prostate. Eighty-five percent (231/273) were further investigated, including with PSA tests (227/231, 98.3%), 3 T mpMRI (68/231, 29.4%), 68 Ga-PSMA PET/CT (33/231, 14.3%), and prostate biopsy (57/231, 24.7%). Results were considered benign in 130/231 (56.3%), indeterminate in 31/231 (13.4%), and malignant in 70/231 (30.3%). PCa was identified in 51/57 (89.5%) of the men who proceeded to biopsy, including 26/27 (96.3%) men with Prostate Imaging Reporting and Data System scores 4-5 mpMRI and six men with a positive 68 Ga-PSMA PET/CT. The most common Gleason score on biopsy was greater than or equal to 4+5 (14/51, 27.5%). 68 Ga-PSMA PET/CT was concordant with the 18 F-FDG findings in 26/33 (78.8%). All 13 men with a positive concordant 18 F-FDG, 3 T mpMRI, and 68 Ga-PSMA PET/CT had PCa on biopsy. There was no statistically significant difference in the 18 F-FDG maximum standardized uptake value between the benign or malignant groups (5.7 vs. 6.1; p =0.580).

CONCLUSION: In this study, after an incidental finding of an avid intraprostatic lesion on 18 F-FDG PET/CT, 70 of the 231 cases (30.3%; 0.8% of the entire cohort) had results consistent with PCa, most commonly as Gleason score greater than or equal to 4+5 disease. Unless there is limited life expectancy due to competing medical co-morbidity, men with an incidental finding of intraprostatic uptake on 18 F-FDG should be further investigated using principles of PCa detection.